Printed circuit board assemblies ("PCAs") with electrical components are used in computers, communications equipment, televisions, and many other products. A PCA typically has a wide variety of electrical components mounted to a printed circuit board ("PCB") to operatively couple the electrical components to desired circuits. The PCB is generally a laminated board with circuit traces on external surfaces of the board or at interlayer levels within the board, and the electrical components are typically light-emitting diodes ("LEDs"), processors, memory devices, clock generators, resistors, cooling units, capacitors and virtually any other type of electrical components. As PCAs become more complex, over 1,000 passive components may be mounted to one side of the PCB. Accordingly, the size of many of the passive components may be as small as approximately 0.080 in.times.0.050 in (a "0805" component) to approximately 0.040 in.times.0.020 in (a "0402" component). Since the electronics manufacturing industry is highly competitive, it is important to quickly and accurately attach a large number of passive components to the PCBs.
Such small passive components generally have very small terminals, and each passive component is typically surface mounted on a PCB to couple each terminal of a component to a contact pad on the PCB. In typical surface mounting techniques, pads of solder paste are deposited onto respective electrical contacts to form multiple solder pads, and adhesive pads are deposited at vacant areas in between the solder pads where components are to be mounted to the PCB. The solder pads and the adhesive pads may be deposited onto the PCB using a stencil printing machine or a pen dispenser known in the art. After the solder pads and adhesive pads are deposited onto the PCB, a pick-and-place machine picks up an electrical component, orients the electrical component to align an appropriate solder pads with the terminals of the component, and then presses the component against the solder pads and at least one corresponding adhesive pad.
Surface mounting components to a PCB, and particularly surface mounting large numbers of small components, raises several manufacturing concerns in PCA manufacturing. One such concern is depositing a sufficient amount of adhesive to adhere a particular component to the PCB without interfering with the electrical contacts on the PCB. In general, a sufficient amount of adhesive must be deposited to withstand 8 pounds of shear force to prevent an attached electrical component from detaching from the PCB, but the adhesive pads cannot spread and interfere with the electrical contacts as the components are pressed against the adhesive pads. Determining the desired volume of the adhesive pads is particularly important for surface mounting small components because the electrical contacts on the PCB are very close to each other. Accordingly, to surface mount small components to a PCB, it is generally necessary to maximize the volume of the adhesive pads without interfering with the electrical contacts between the PCB and the components.
A significant problem in PCA manufacturing is determining the appropriate shape and volume of the adhesive pads to attach components to a PCB without interfering with the electrical contacts of the PCA. Conventional PCA manufacturing processes determine the shape and volume of the adhesive pads on a trial-and-error basis by mounting a component to a PCB and then testing whether the component is operatively coupled to the PCB and can withstand 8 pounds of shear force. It will be appreciated that conventional trial-and-error testing is time-consuming and may tie up the PCA assembly line for a significant period of time while different shapes and volumes of adhesive pads are tested. Such down-time associated with conventional trial-and-error adhesive pad testing is particularly problematic in contract PCA manufacturing in which several different configurations of PCAs with different adhesive pad parameters may be manufactured in a single day. Thus, it would be desirable to develop an apparatus and method for determining the desired volume and/or shape of each adhesive pad to be deposited onto a printed circuit board in PCA manufacturing.